The invention relates to water heaters, and more particularly to water heaters adapted to be mounted on the roof of a building.
It is known to provide a water heater within a building, and to mount other equipment (e.g., HVAC equipment) on the roof of a building. A primary concern with rooftop equipment is the load imposed on the roof by the weight of the equipment. Most rooftop equipment is supported on the roof by a roof curb. The roof curb provides a weather-tight seal between the equipment and the roof, and distributes the weight load of the equipment to the building""s roof. The roof curb also prevents leakage of water into the building and equipment in the event of a roof flood. Roof curbs are typically built to match the pitch of the roof so that the equipment mounts on a level surface. Rooftop equipment is typically raised to the roof with a crane and set on the roof curb. A foam sealing tape is often used between the bottom of the equipment and the roof curb to provide a weather-tight seal.
Many commercial buildings include a wall around the rooftop to screen the rooftop equipment from view. Much of the HVAC equipment currently installed on rooftops is enclosed in a rectangular cabinet, and has a sufficiently low profile to be not visible from the ground level.
The present invention identifies several advantages to providing a water heater on the roof of a building. In commercial applications, one factor affecting many aspects of some businesses, and particularly retail and restaurant businesses, is floor space. Moving a water heater out of a building and positioning it on the building""s roof may permit more floor space to be used for conducting business. In addition to potentially freeing up floor space and the need for a separate boiler room in a building, the present invention provides other advantages over interior water heaters. For example, the design of interior water heaters must account for such considerations as flooding, CO generation, interior noise, some fire hazards arising from flammable vapors, building depressurization, and exhaust venting. While interior water heaters are sometimes limited to a significant degree by such design concerns, a rooftop water heater embodying the present invention is typically not affected to the same extent. This may make design and maintenance of the rooftop water heater simpler and cheaper in some instances when compared to the design and maintenance of interior water heaters.
Several design parameters are imposed on the design of a rooftop water heater by weather conditions and the expectations of potential purchasers of such water heaters. The water heater must first account for weather conditions not normally encountered by interior water heaters. It would be desirable to mount the water heater on a weather-tight roof curb that would support the water heater above expected water levels in the event of a roof flood. The roof curb would also provide the required weight load distribution to the roof. Because roof curbs are already used to support other rooftop equipment, it is convenient to use a roof curb to support a rooftop water heater as well.
To maintain the aesthetics of their buildings, purchasers would likely want equipment that cannot be ordinarily seen from the ground level. The water heater therefore must have a sufficiently low profile and be of substantially the same height as most HVAC equipment to meet the expected demands of purchasers.
In light of the foregoing considerations, the present invention provides a rooftop water heater that includes a water tank mounted on a base member which is in turn mounted on a roof curb. The base member includes a drain communicating with the building""s sewage system so that water leaking or otherwise flowing out of the water tank is drained away from the water heater without causing damage to the roof or the water heater itself. A pair of rails may be mounted under the base member such that the water heater and base member may be moved with a fork lift. The rails also include holes for accepting the hooks of a lifting crane for raising the water heater to the roof of the building.
The water tank is preferably generally cylindrical in shape with a longitudinal axis extending substantially horizontally. In this regard, the tank has a low profile compared to a tank having its longitudinal axis extending vertically. A head encloses one end of the tank. A plurality of water pipes extend up through the roof curb and through a water pipe aperture in the base member. A vertical wall surrounds the water pipe aperture. A grommet fits over the vertical wall and seals the water pipes with respect to the base member.
A plurality of panels, including a cabinet door and a top, are preferably interconnected with and supported by the base member to substantially weather-tightly enclose the water tank. The top and cabinet door may be removed from the other panels to permit access to the water tank.
A U-shaped flue tube is preferably contained within the water tank. A baffle or turbulator is positioned within one of the legs of the U-shaped flue tube. The ends of the flue tube extend through the head of the tank. The legs each include a longitudinal axis, and the longitudinal axes together define a flue plane that may be disposed substantially vertically, or may be angled with respect to vertical. Preferably, the flue plane is angled in the range of 30-60xc2x0 with respect to vertical.
The water heater also includes inlet and outlet tubes for providing cold water to the tank and drawing hot water from the tank, respectively. The inlet and outlet tubes extend substantially the entire inside length of the tank, and preferably include a plurality of apertures facing in a single direction. The outlet tube is positioned in the top portion of the tank with its apertures facing up while the inlet tube is positioned in the bottom portion of the tank with its apertures facing down. Preferably, the inlet and outlet tubes extend through the head of the tank, but in an alternative construction, the inlet and outlet tubes include elbows that extend through the tank shell.